Method and apparatus for washing in particular items of laundry

ABSTRACT

A method and apparatus for washing items of laundry that makes provision to continuously filter the treatment liquid during the washing operation. As a result, interfering attendant materials in and on the treatment liquid are successively removed during the washing operation, which increases the efficacy of the washing operation. Provision is preferably made to remove both lighter constituents, such as foam and lint, from the treatment liquid and also to filter heavier constituents, such as impurities washed out of the items of laundry, from the treatment liquid using the same filter. The same filter can also be used, after the end of the washing operation, to filter the treatment liquid to be let out and to temporarily store the treatment liquid in a collecting tank before the filtered treatment liquid is reused. The invention thus permits multiple functions of the filter.

STATEMENT OF RELATED APPLICATIONS

This patent application claims priority on and the benefit of German Patent Application No. 10 2011 013 806.4 having a filing date of 14 Mar. 2011.

BACKGROUND OF THE INVENTION

1. Technical Field

The invention relates to a method for washing in particular items of laundry, the items of laundry being at least washed with a treatment liquid in a rotationally drivable drum and the treatment liquid being removed from the drum as required by means of at least one outer drum assigned at least to part of the drum. Furthermore, the invention relates to an apparatus for washing in particular items of laundry, with a rotationally drivable drum and at least one stationary outer drum which extends at least over part of the length of the drum.

2. Prior Art

The washing, namely the actual laundering and the rinsing, of all types of objects, in particular items of laundry, is undertaken in washing machines which have a rotationally driveable drum which is assigned at least one stationary and liquid-tight outer drum. The at least one outer drum extends over at least part of the drum, in particular part of the length of the rotationally driveable drum. The washing is undertaken using a treatment liquid, which optionally has treatment additives, in the drum. The treatment liquid takes up only a lower part of the drum. The level, i.e. the surface of the treatment liquid, preferably lies somewhat below the axis of rotation of the drum. Where the drum is assigned an outer drum, the treatment liquid is also located in the liquid-tight outer drum. By means of a perforation in the rotationally driveable drum in the region of the respective outer drum, the treatment liquid in the outer drum can enter the lower region of the rotating drum where the treatment liquid comes into contact with the objects to be washed, in particular items of laundry, which are located in the rotating drum.

As a consequence of the drum executing full circle rotations or opposed part circle rotations (pivoting movements) during the washing, foaming occurs, caused especially by the treatment additives in the treatment liquid. The foam accumulates with lint at least partially combined therewith from the laundry to be washed on the surface of the treatment liquid. In addition, the treatment liquid absorbs dirt washed out of the laundry and possibly foreign materials which, for the most part, are heavier than the treatment liquid and therefore collect in the bottom region of the outer drum. The foam and the dirt impair the efficacy of the washing operation.

BRIEF SUMMARY OF THE INVENTION

The invention is based on the object of providing a method and an apparatus for more effectively washing and/or rinsing items of laundry and other objects.

A method for achieving this object is a method for washing in particular items of laundry, the items of laundry being at least washed with a treatment liquid in a rotationally drivable drum and the treatment liquid being removed from the drum as required by means of at least one outer drum assigned at least to part of the drum, wherein, during at least the washing, the treatment liquid is filtered outside the drum and the at least one outer drum. According thereto, the treatment liquid, preferably always only some of the treatment liquid, is filtered during the treatment, i.e. in particular the washing and rinsing of the items of laundry or other objects, outside the drum and the at least one outer drum assigned thereto. Since the filtering is undertaken during the washing operation, attendant materials which impair the washing operation are successively removed from the treatment liquid. The washing can then be undertaken more effectively because of the lower loading of the treatment liquid by the attendant materials. The washing operation is not impaired by the filtering outside the washing machine.

The filtering of the treatment liquid is preferably undertaken continuously during the washing. As a result, attendant materials, in particular foam, lint, dirt residues and the like, which are newly collected in the treatment liquid as the washing operation proceeds are gradually filtered out, preferably continuously, in particular during the entire washing operation.

Provision is preferably made for the continuous filtering of the treatment liquid to be undertaken in a manner such that the treatment liquid is successively circulated by being pumped through or via the filter. As a result, some of the treatment liquid is always subjected to filtering while the rest, especially a large part, of the treatment liquid remains in the outer drum of the rotationally driveable drum and therefore, despite the successive and/or continuous filtering of some of the treatment liquid being undertaken at the same time, the washing operation is maintained without a loss in performance.

In an advantageous development of the invention, a continuous stream of the treatment liquid is let out of the outer drum at at least one outlet and, after filtering, said treatment liquid is returned again to the outer drum. As a result, a small part of the treatment liquid is constantly circulated past the filter and the filter is continuously subjected to treatment liquid to be filtered. The volumetric stream of treatment liquid which is conducted via the filter is selected so as to correspond to the efficiency of the filter and the amount of treatment liquid remaining in the outer drum and in the drum containing the laundry to be treated is not significantly reduced, and therefore the level of the treatment liquid in the drum does not fall below the desired level.

According to a preferred development of the method, lighter and heavier constituents are optionally, in particular alternately, filtered out of the treatment liquid. Therefore, constituents, such as foam, lint or the like, collecting on the surface of the treatment liquid and heavier constituents, such as dirt particles, foreign materials or the like, dropping onto the bottom of the outer drum can be gradually filtered out from the treatment liquid. It is alternatively also conceivable simultaneously to remove a mixture of treatment liquid containing lighter constituents and heavier constituents from the outer drum and to filter said constituents together.

Preferably, in order to filter out lighter constituents from the treatment liquid, the treatment liquid, with the lighter constituents in the region of the surface thereof, specifically on the surface or just below the surface, is removed from the outer drum while the treatment liquid, with the heavier constituents below the surface of the treatment liquid, especially on the bottom or in the region of the bottom of the outer drum, is removed from same. By means of the various options for removing the treatment liquid to be filtered from the outer drum, the filter has a plurality of functions by being able to filter out lighter and heavier constituents, in each case separately or else together, from the treatment liquid.

Provision is preferably made also to use the at least one filter in order to filter treatment liquid to be let out of the outer drum at the end of the washing operation. This provides a further option for using the same filter. The treatment liquid to be let out of the outer drum can also be completely filtered by filtering outside the outer drum. The filtered treatment liquid is preferably conducted into a storage tank. The filtered and used treatment liquid can be supplied from the collecting or storage tank for suitable reuse.

According to a further preferred refinement of the method, the treatment liquid is filtered by a gravity filter. The treatment liquid can thus flow freely through the filter, wherein the filtered treatment liquid is separated from the filtered-out constituents by gravity. As an alternative or in addition, provision may be made to allow the liquid to flow in a freely flowing manner by means of gravity to the filter. The filter is thereby uniformly subjected to the treatment liquid following the gravity action and the filtering is likewise undertaken. In this case, however, it is conceivable for the flow rate or the amount of treatment liquid supplied to the filter per unit of time to be able to be set or changed by, for example, an adjustable throttle valve in a feed line to the filter. The treatment liquid supplied to the filter per unit of time can thus be matched to the efficiency of the filter and optimum filtering thus brought about.

An apparatus for achieving the object referred to at the beginning, the apparatus preferably being a washing machine, is an apparatus for washing in particular items of laundry, with a rotationally drivable drum and at least one stationary outer drum which extends at least over part of the length of the drum, wherein a circulating line having at least one filter is assigned to at least one outer drum. Owing to the fact that a circulating line having a filter is assigned to at least one outer drum, the treatment liquid can be filtered, specifically in particular continuously, during the washing operation, namely the pre-washing, clear washing and/or rinsing. As a result, treatment liquid which is at least partially freed from constituents impairing the washing operation, especially foam, is always available for the washing operation.

The circulating line is preferably provided with a plurality of outflows, in particular outflows which can be shut off individually, from the respective outer drum. In this case, an upper outflow is in particular arranged in the region of the level of the treatment liquid in the drum and in the outer drum while another outflow is preferably provided in the region of the bottom or in the bottom of the outer drum. This enables both treatment liquid with attendant materials swimming thereon in the region of the surface of the treatment liquid and also treatment liquid with dropping attendant materials to be removed from the outer drum. The capability of shutting off at least one outflow makes it possible to remove treatment liquid from the outer drum selectively from the top or from the bottom or, if desired, also to remove treatment liquid with floating and dropped attendant materials at the same time from the outer drum.

Another advantageous refinement of the apparatus makes provision to provide at least one pump in the circulating or circulation line downstream of the at least one filter, preferably as seen in the direction of flow of the treatment liquid. By means of the pump, the filtered liquid can be pumped back into preferably the same outer drum from which the treatment liquid was removed, optionally also a different outer drum, even if the position of the introduction of the filtered liquid into the outer drum is located higher than the filter.

Provision may be made for the circulating line to be connected, preferably downstream of the pump, to an inflow, which can be preferably shut off, to the outer drum. The capability of shutting off the inflow makes it possible to pump filtered treatment liquid to a different location. For example, the circulating line can have an outflow, to which at least one collecting tank is preferably assigned. The outflow may be located upstream of the pump, as seen in the direction of flow, if the filtered treatment liquid can be conducted away by gravity. By contrast, it is expedient to arrange the outflow downstream of the pump in the direction of flow if the filtered treatment liquid has to be pumped to the outflow located higher.

In a preferred apparatus, the at least one filter is designed as a gravity filter. This filter operates automatically. Above all, the treatment liquid to be filtered does not need to be pumped through the gravity filter by a pump. On the contrary, the treatment liquid can flow automatically on account of the potential energy thereof out of the outer drum to the filter and through or via the latter. A filter of this type may be designed as a sieve, through the opening in which the treatment liquid to be filtered flows, but heavier and lighter attendant materials are retained, and therefore said attendant materials can be removed on the filtering surface which is formed by the sieve and can have a rectilinear, oblique and/or curved profile.

In order to clean the filtering surface, in particular the filter sieve, said filtering surface can be subjected to a flowing fluid, for example by means of spray nozzles under the preferably sieve-like filtering surface.

The invention is suitable particularly for apparatuses designed in the manner of commercial washing machines, namely what are referred to as continuous process washing machines. A washing machine of this type has an elongate, overall rotationally driveable drum with a plurality of consecutive chambers, at least one of the chambers being assigned an outer drum. An outer drum is customarily located where treatment liquid, such as pre-washing liquid, clear washing liquid and/or rinsing liquid, can be conducted out of the drum or liquids can be supplied to the drum. By means of the assignment of the outer drum to at least one chamber, the invention makes it possible, in a chamber-related manner in a continuous process washing machine, always preferably to continuously filter only the treatment liquid present in the relevant chamber during the washing operation, specifically in particular to at least partially remove both lighter constituents and also heavy constituents successively, but constantly, especially continuously, from the treatment liquid in the relevant chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred exemplary embodiment of the invention is explained in more detail below with reference to the drawing, in which:

FIG. 1 shows a schematic side view of an apparatus according to the invention in the form of a continuous process washing machine.

FIG. 2 shows a cross section through a chamber, which is provided with an outer drum, of the continuous process washing machine from FIG. 1 in a schematic illustration.

FIG. 3 shows a cross section analogously to FIG. 2 in a different manner of operation.

FIG. 4 shows a cross section analogously to FIG. 2 in yet another manner of operation.

FIG. 5 shows a longitudinal section through a filter merely illustrated schematically in FIGS. 1 to 4.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention is described below with reference to an apparatus, in the form of a continuous process washing machine 10, for washing and rinsing items of laundry. However, the invention is not restricted thereto.

The continuous process washing machine 10 shown schematically in FIG. 1 has a cylindrical drum 12 which is rotationally driveable about a preferably horizontal axis of rotation 11. The axis of rotation 11 lies on the longitudinal center axis of the drum 12. The laundry to be washed is transported from the left to the right (with respect to FIG. 1) in the treatment direction 13 through the rotationally driven drum 12.

A plurality of chambers 15 which are consecutive in the treatment direction 13 are formed by transversely directed partitions 14 in the drum 12. One laundry batch is treated, in particular washed and rinsed, in each chamber 15. The chambers 15 may be identical in size, but may also differ in size. The partitions 14 have central or eccentric openings (located at the edge) which are not shown in the figure. Through the openings, the laundry can be transferred batchwise in the treatment direction 13 from one chamber 15 into the following chamber 15. The continuous process washing machine 10 shown in FIG. 1 has twelve chambers 15. However, the invention is not restricted thereto. The continuous process washing machine 10 may have a larger or smaller number of chambers 15.

The first four chambers 15, as seen in the treatment direction 13, form a pre-washing zone 16 in the continuous process washing machine 10 shown. The following five chambers 15 form a clear washing zone 17. A rinsing zone 18 having three consecutive chambers 15 follows the clear washing zone 17, as seen in the treatment direction 13. The pre-washing zone 16, clear washing zone 17 and rinsing zone 18 may have a number of chambers 15 differing from the exemplary embodiment (shown in FIG. 1) of the continuous process washing machine 10. It is also conceivable for at least one further chamber (not illustrated in FIG. 1) to follow the rinsing zone 18 in order to form a finishing zone. The rinsing zone 18 may also be omitted.

In the continuous process washing machine 10 shown here, the final chamber 15 of the pre-washing zone 16, the clear washing zone 17 and the rinsing zone 18 has in each case an outer drum 19. In addition, an outer drum 19 is assigned to the first chamber 15 of the clear washing zone 17 and the rinsing zone 18. All of the outer drums 19 are designed to be equally impermeable to liquid. So that treatment liquid for the laundry in the outer drum 19 can communicate with that section of the drum 12 which extends over the relevant chamber 15 with an outer drum 19, the drum 12 is designed to be at least partially permeable for treatment liquid, in particular is perforated, in regions of those chambers 15 which are assigned an outer drum 19. As a result, treatment liquid can enter the liquid-permeable section of the drum 12, which section is assigned to the chamber 15, from the respective outer drum 19, and vice versa. The treatment liquid in the respective chamber 15 has a desired level. The level is preferably somewhat below the axis of rotation 11 (FIGS. 2 and 3). Consequently, the surface of the treatment liquid in the relevant chamber 15 is also located somewhat below the axis of rotation 11.

The lower region of each of the outer drums 19 of identical design preferably has an expanded portion preferably designed in the manner of a terminal box. Said expanded portion accommodates a stock of treatment liquid below the drum 12.

Constituents which are lighter than the treatment liquid, for example foam, lint and the like, collect on the surface of the treatment liquid. The lint is preferably at least for the most part combined in the foam. Solid constituents of the treatment liquid that are heavier than the treatment liquid can collect on a bottom 20 of the outer drum 19, which is expanded at the bottom in order to form the terminal box. The heavier constituents are dirt and other solids washed out of the laundry, for example small foreign bodies which can pass through the perforation in the drum 12 in the region of the respective chamber 15 with the outer drum 19.

In the case of the continuous process washing machine 10 shown here, the outer drum of the final chamber of the clear washing zone 17 and the outer drum 19 of the final chamber 15 of the rinsing zone 18 are each assigned a circulating line 21 with a filter 22. The latter are of identical design at the end of the clear washing zone 17 and at the end of the rinsing zone 18. Both the circulating line 21 and the respective filter 22 are located outside the drum 12 and the outer drum 19. The respective filter 22 and the circulating line 21 assigned thereto are preferably assigned, in particular fastened, to a rack 23 of the continuous process washing machine 10. However, the filters 22 may also be located at a different location in the laundry away from the continuous process washing machine 10. A pump 24 is provided downstream of the or each filter 22, as seen in the direction of flow of the treatment liquid through the circulating line 21, in order to pump the filtered treatment liquid back into the respective outer drum 19.

FIGS. 2 to 5 show in more detail the circulating line 21 and the filter 22 assigned thereto in the region of the final chamber 15 of the clear washing zone 17. The circulating line 21 and the filter 22 in the region of the outer drum 19 of the final chamber 15 of the rinsing zone 18 are designed in the same manner.

In particular, FIG. 2 shows that the circulating line 21 is divided, namely consists of a starting part, as seen in the direction of flow to the filter 22, and a return part emerging from the filter 22. As a result, the circulating line 21 is interrupted in the region of the filter 22, but the starting part and the return part of the circulating line 21 are connected in terms of flow by the filter 22. In addition, the starting part of the circulating line 21 is designed in two strands, namely has a first starting part 25 and a second starting part 26. The first starting part 25 of the circulating line 21 is connected to an outflow 27 of the outer drum 19, the outflow being located in the region of the level or the surface of the treatment liquid in the chamber 15 to which the outer drum 19 is assigned. The second starting part 26 of the circulating line 21 is connected to a second outflow 28 in the bottom region, in particular in the vicinity of the bottom 20, of the outer drum 19 of the final chamber 15 of the clear washing zone 17. The outflow 28 may also be provided in the bottom 20 of the outer drum 19. Both starting parts 25 and 26 end upstream of the filter 22. The return part of the circulating line 21 is assigned to that side of the filter 22 on which the filtered treatment liquid is obtained. The filtered liquid is pumped back into the outer drum 19 by the pump 24 in the return part of the circulating line 21. For this purpose, an inlet 29 is provided for connecting a rear end of the return part of the circulating line 21 to the outer drum 19 below the surface of the treatment liquid.

A discharge line 30 branches off from the return part of the circulating line 21 downstream of the pump 24, the discharge line leading to a collecting tank 31 or opening into the collecting tank 31.

The second starting part 26 of the circulating line 21 is assigned a valve 32. This is preferably an adjustable throttle valve with which the flow rate of the treatment liquid through the second starting part 26 can be changed, but the second starting part 26 may also be closed. In this way, the inflow of treatment liquid from the bottom region of the outer drum 19 to the filter 22 can be entirely prevented or changed in respect of the volumetric stream of the treatment liquid to the filter 22 per unit of time, for example for adaptation to the capacity of the filter 22. Similarly, if required, a simple shut-off valve or an adjustable throttle valve may be arranged in the first starting part 25 of the circulating line 21. It is then possible for partial streams from the surface of the treatment liquid and from the bottom of the outer drum 19 to be conducted in a directed manner to the filter 22 at the same time and for the flow rate of the treatment liquid through the first starting part 25 to be changed and optionally for the first starting part 25 of the circulating line 21 also to be completely closed. A further valve 33 is located in the return part of the circulating line 21, specifically downstream of the branching off of the discharge line 30 form the circulating line 21, as seen in the direction of flow of the treatment liquid. A valve 34 is also assigned to the discharge line 30. By means of the valves 33 and 34, the outflow of the filtered treatment liquid can be controlled in a directed manner, specifically either back to the outer drum 19 or into the collecting tank 31.

The filter 22 is illustrated in detail in FIG. 5. This involves what is referred to as a gravity filter, in which the treatment liquid to be filtered is caused by gravity to flow through a filter sieve 31, specifically from the upper side of the filter sieve 48 to the lower side thereof. This may also be undertaken during the flow of the treatment liquid to be filtered along on the filter sieve 48. The filter sieve 48 is arranged in a preferably completely closed housing 35. The upper side of the housing 35 may optionally be open. The housing 35 has (as seen from the side) an oblique profile with an oblique bottom 36. From above, the ends of the two starting parts 25 and 26 of the circulating line 21 are guided at the highest point into the oblique housing 35. The filter sieve 48 is likewise fastened in an obliquely directed manner in the housing 35 at a distance from the bottom 36. As a result, the filter sieve 48 divides the housing 35 into an upper part 37 located above the surface of the filter sieve 34 and a lower part 38 located below the filter sieve 48. The filter sieve 48 may be formed from a perforated sheet with a uniform grid of passage holes of corresponding size or from a wire cloth with a corresponding mesh width.

The filter sieve 48 is preferably designed in two layers. Said filter sieve 48 consists of a lower, stable and large-meshed supporting lattice and a fine-meshed sieve which is arranged above the latter and is designed in the manner of a lattice or is braided. The optionally flexible sieve is then supported by the supporting lattice.

The filter sieve 48 ends at a distance upstream of a transverse wall 39 at the lower end of the housing 35. A height-adjustable, transversely directed weir 40 is located upstream of the end of the filter sieve 37. By appropriate height adjustment of the plate-like weir 40 a gap of corresponding width for conducting away the constituents filtered out of the treatment liquid is produced above the end of the lint sieve 34. A pivotable flap may also be provided instead of the height-adjustable weir 40. A chamber 42 for collecting the constituents filtered out of the treatment liquid is located between that end of the filter sieve 48 which is spaced apart from the transverse wall 39 and is formed by a lower transverse edge 41 of same. A collecting container 43 for filtered-out constituents can be provided in the chamber 42. The collecting container 43 can preferably be removed from the chamber 42 or can be withdrawn from the chamber 42 in the manner of a drawer.

At the bottom end region upstream of the transverse wall 39, the bottom 36 of the housing 35 has a depression which forms a sump 44. During the emptying of the filter 22, the remaining filtered treatment liquid collects in the sump 44 as the lowermost point of the housing 35. In addition, the sump 44 forms a pump reservoir which ensures that, during operation of the filter 22, the pump 24 is constantly supplied with sufficiently filtered treatment liquid. In addition, a float switch 45 serving to prevent dry operation of the pump 24 is provided in the sump 44. Furthermore, a closable outflow 46 is located at the lowermost point of the sump 44. When the outflow 46 is opened, the treatment liquid can be completely let out of the housing 35 of the filter 22.

A plurality of cleaning nozzles 47 directed toward the lower side of the filter sieve 48 are provided in the lower part 38 of the housing 35. The cleaning nozzles 47 are distributed in the lower part 38 in such a manner that they can subject the entire lower side of the filter sieve 48, or at least a large part thereof, to cleaning liquid. The cleaning liquid is preferably fresh water. However, filtered treatment liquid from the collecting tank 31 may also be used. The used cleaning liquid is then pumped back again into the collecting tank 31 through the return part of the circulating line 21 and the discharge line 30 or conducted into an outflow.

The method according to the invention is described in more detail below with reference to the previously described apparatus, namely the continuous process washing machine 10.

The method according to the invention makes provision, on the basis of the respective chamber 15 with an outer drum 19, to preferably continuously filter the treatment liquid outside the outer drum 19 during the washing operation. The treatment liquid from each outer drum 19 or else only selected outer drums 19 or from only one outer drum 19 can be filtered. The filtration can be undertaken periodically during the washing operation, but also continuously during the entire washing operation. With the filtration during the washing operation, a small amount of the treatment liquid, which is continuously removed from the treatment liquid, is pumped through the circulating line 21 by the pump 24 and, in the process, is filtered by the filter 22, which is designed as a gravity filter, in accordance with the principle of gravity. Only such a small part of the treatment liquid at a time is subjected to the filtering that the provided treatment liquid level in the drum 12 receiving the items of laundry to be washed and in the outer drum 19 is maintained. In the exemplary embodiment shown, the level of the treatment liquid in the drum 12 is selected such that the surface 49 of the treatment liquid lies somewhat below the axis of rotation 11 of the drum 12 (FIGS. 2 to 4).

The flow rate of the treatment liquid through the circulating line 21 is selected or set at the throttleable valve 32 in such a manner that, over the course of a treatment operation of the batch of laundry in the relevant chamber 15, the treatment liquid in said chamber 15 is completely circulated at least once and filtered by the filter 22.

The method according to the invention is designed in such a manner that it permits a multiple function of the filter 22. Accordingly, the filter 22 is used in order to carry out different filtering tasks which are illustrated schematically in FIGS. 2 to 4.

FIG. 2 shows the use of the filter 22 for removing those constituents from the treatment liquid that are lighter than the treatment liquid, for example foam, in particular foam together with entrained lint. The possibly lint-containing foam collects on the surface 49 of the treatment liquid in the drum 12. Via the outflow 27, which is located in the region of the surface 49 of the treatment liquid, the foam containing lint and other lighter constituents is removed together with the treatment liquid located on the surface 49 from the drum 12 and the outer drum 19 and fed to the filter 22 via the first starting part 25 of the circulating line 21. In the process, the treatment liquid with the lighter components passes into the upper part 37 of the housing 35 of the filter 22. As a result of the oblique position of the filter sieve 48, the treatment liquid to be filtered flows together with the lighter constituents to be filtered out along the filter sieve 48. By means of gravity, only the treatment liquid passes through the filter sieve 48, and said treatment liquid thus passes filtered into the lower part 38 of the housing 35 of the filter 22. The filtered treatment liquid is then pumped by the pump 24 through the circulating line 21, with the valve 33 open, to the inlet 29 in the outer drum 19 and therefore the filtered treatment liquid is supplied again to the washing process, namely to the outer drum 19 and the drum 12.

The filtered-out lighter constituents of the treatment liquid flow along the oblique filter sieve 48. Through the gap below the transverse edge 41 of the weir 40, said filtered-out lighter constituents, in particular foam and lint, enter the collecting container 43 of the filter 22. The collecting container 43 collects lint, in particular, which can be disposed of from time to time by the collecting container 43 being withdrawn or removed from the chamber 42 of the housing 35 of the filter 22. Other constituents can be collected at another point of the chamber 42 and removed from there, for example into an outflow.

The valves 32 and 34 are closed during the previously described filtering off of lighter constituents from or out of the treatment liquid. Only light constituents are then separated from the treatment liquid, and the filtered treatment liquid is continuously pumped back circulating through the circulating line 21 into the continuous process washing machine 10. As a result, cleaned treatment liquid is continuously supplied again to the treatment liquid, and therefore the quantity of treatment liquid in the relevant chamber 15 always remains substantially the same and is reduced only by the treatment liquid located in the circulating line 21 and in the region of the filter 22. By means of the filtering off of foam, which is undertaken during the washing operation, with light constituents combined thereon or therein, the foam carpet on the treatment liquid is reduced and the washing action thereby increased, as a result of which stains especially can be more effectively removed from the laundry. It is also conceivable to temporarily close the weir 40 or the pivotable flap for certain time intervals during the filtering out of the foam with the light constituents combined therein and to subject the foam in the region of the filter 22 to water, preferably fresh water. As a result, the foam is destroyed, as it were, and the quantity of foam reduced.

FIG. 3 schematically illustrates a second intended use of the filter 22. Here, the valve 32 in the second starting part 26 of the circulating line 21 is opened or adjusted to such an extent that the treatment liquid can be supplied continuously to the filter 22 during the washing of the laundry. In this case, the valve 32, which is preferably designed as a throttle valve, is adjusted in such a manner that only a desired volumetric stream of the treatment liquid flows through the circulating line 21. The treatment liquid enters the second starting part 26 through the outflow 28 arranged in the vicinity of the bottom 20 of the outer drum 19. In this case, with the treatment liquid, heavier constituents thereof, for example dirt particles removed form the laundry, but also other small solid particles and possibly foreign bodies, pass via the outflow 28 and the second starting part 26 of the circulating line 21 to the filter 22. The solid constituents are filtered out here from the treatment liquid by gravity by the solid constituents being retained by the filter sieve 48 and only the treatment liquid flowing through the filter sieve 48 and, in the process, being filtered. The filtered treatment liquid is pumped back again via the circulating line 21 through the inlet 29 into the outer drum 19. Filtered-out solid constituents are removed laterally above the filter sieve 48 as a result of the oblique arrangement of same and are collected in the chamber 42 of the housing 35 of the filter 22. Like lint, the solid constituents can also be collected in the collecting container 43.

In the exemplary embodiment shown, the first starting part 25 of the circulating line 21 cannot be shut off by a valve. Constituents floating on the surface 49 of the treatment liquid are therefore continuously conducted through the first starting part 25 of the circulating line 21 to the filter 22. By contrast, only treatment liquid with heavier constituents contained therein, if this is desired, flows through the second starting part 26 of the circulating line 21 as a result of the valve 32 which is assigned to said circulating line and can be shut off and throttled. For example, the valve 32 may be opened only periodically during the washing. However, the valve 32 may also be opened continuously, the throttle allowing only as much treatment liquid to be guided through the second starting part 26 to the filter 22 as the filter capacity permits. However, it is also conceivable likewise to assign a valve to the first starting part 25 of the circulating line 21. If said valve is closed, with the valve 25 in the second starting part 26 open, only treatment liquid with heavier constituents contained therein can be supplied to the filter 22 and the treatment liquid freed from heavier constituents by said filter.

FIG. 4 shows the method according to a third manner of operation of the filter 22. The treatment liquid is filtered here when the treatment liquid is completely let out of the chamber 15. This is the case when a bath change, i.e. an exchange of the treatment liquid, is undertaken in the relevant chamber 15. Such a bath change is preferably undertaken after the washing of the items of laundry in the relevant chamber 15 when the laundry batch is transferred from the chamber 15 into the next chamber 15 in the treatment direction 13, for example the first chamber 15 of the rinsing zone 18, or in order to unload the completely washed and rinsed laundry batch from the continuous process washing machine 10.

When the treatment liquid is let out, the valve 32 in the second starting part 26 of the circulating line 21 and a possible valve in the first starting part 25 are preferably fully open. The treatment liquid can then be entirely let out of the drum 12 and out of the outer drum 19 assigned to the latter. The treatment liquid to be let out is filtered by the filter 22 and the filtered treatment liquid is subsequently conducted by the pump 24 through the circulating line 21, with the valve 34 in the discharge line 30 open, into the collecting tank 31. The following valve 33 in the circulating line 21 in the direction of flow of the treatment liquid through the circulating line 21 to the discharge line 30 is then preferably closed.

The lower sump 44 in the housing 35 of the filter 22 makes it possible to conduct the treatment liquid out of the filter 22 through the outflow 46 without leaving a residue. However, only the remaining treatment liquid collecting at the bottom in the sump 44 and being unable to be pumped by the pump 24 into the collecting tank 31 leaves the outflow 46. As a consequence of the complete emptying not only of the outer drum 19 but also of the filter 22, mixing of the treatment liquid of the washing operation which has taken place last with possibly different treatment liquid for the next washing operation is avoided.

If the treatment liquid is completely let out of the drum 12 and the outer drum 19, cleaning of the filter sieve 48 preferably takes place with the filter 22 currently not carrying out any filtering. This is undertaken from the lower side of the filter sieve 48 by means of the cleaning nozzles 47 which are directed at said lower side. For this purpose, the cleaning nozzles 47 can be supplied with fresh water or cleaned treatment liquid from the collecting tank 31 as the cleaning liquid. The soiled cleaning liquid obtained during the cleaning of the filter sieve 48 is conducted away below the filter sieve 48, i.e. in the lower part 38. The cleaning liquid collects in the sump 44 at the lowermost point of the housing 35 of the filter 22 and is completely conducted away therefrom through the outflow 46 and subsequently disposed of. The filter 22 may also be cleaned in order to destroy the foam or reduce the quantity thereof during the manner of operation of the filter 22 according to FIG. 2.

The method operates in the above-described manner both in the region of the final chamber 15 of the clear washing zone 17 and of the final chamber 15 of the rinsing zone 18. It is optionally also possible for the method to be carried out at the final chamber 15 of the pre-washing zone 16. The above-described method is also suitable for continuous process washing machines which only have a pre-washing zone 16 and a clear washing zone 17, but not a rinsing zone 18.

The invention is suitable not only for all types of continuous process washing machines but also for other washing machines and washing machines for washing and cleaning any other objects, i.e. not only items of laundry.

LIST OF REFERENCE NUMBERS

-   10 Continuous process washing machine -   11 Axis of rotation -   12 Drum -   13 Treatment direction -   14 Partition -   15 Chamber -   16 Pre-washing zone -   17 Clear washing zone -   18 Rinsing zone -   19 Outer drum -   20 Bottom -   21 Circulating line -   22 Filter -   23 Rack -   24 Pump -   25 First starting part -   26 Second starting part -   27 Outflow -   28 Outflow -   29 Inlet -   30 Discharge line -   31 Collecting tank -   32 Valve -   33 Valve -   34 Valve -   35 Housing -   36 Bottom -   37 Upper part -   38 Lower part -   39 Transverse wall -   40 Weir -   41 Transverse edge -   42 Chamber -   43 Collecting container -   44 Sump -   45 Float switch -   46 Outflow -   47 Cleaning nozzle -   48 Filter sieve -   49 Surface 

1. A method for washing items of laundry, comprising: at least washing the items of laundry with a treatment liquid in a rotationally drivable drum (12), removing the treatment liquid from the drum (12) as required by means of at least one outer drum (19) assigned at least to part of the drum (12), and during at least the washing, the treatment liquid is filtered outside the drum (12) and the at least one outer drum (19).
 2. The method as claimed in claim 1, wherein the filtering is undertaken continuously during at least part of the duration of the washing process.
 3. The method as claimed in claim 1, wherein only some of the treatment liquid is continuously constantly circulated through a filter (22).
 4. The method as claimed in claim 2, wherein only some of the treatment liquid is continuously constantly circulated through a filter (22).
 5. The method as claimed in claim 1, further comprising continuously withdrawing an amount of treatment liquid from the respective outer drum (19) at at least one outflow (27, 28) and, after filtering, returning said treatment liquid again to the same outer drum (19).
 6. The method as claimed in claim 1, further comprising optionally or alternately filtering constituents which are lighter or heavier than the treatment liquid out of the treatment liquid.
 7. The method as claimed in claim 1, further comprising, in order to filter out lighter constituents from the treatment liquid, removing the treatment liquid, with the lighter constituents on the surface thereof, from the outer drum (19) and, in order to filter out heavier constituents of the treatment liquid, removing the treatment liquid, with the heavier constituents below the surface of the treatment liquid, from the outer drum (19).
 8. The method as claimed in claim 1, further comprising conducting treatment liquid to be let out of at least one outer drum (19) through or via the same filter (22).
 9. The method as claimed in claim 1, further comprising collecting the filtered treatment liquid by at least one collecting tank (31).
 10. The method as claimed in claim 1, further comprising filtering the treatment liquid by a filter (22) designed as a gravity filter.
 11. An apparatus for washing items of laundry, comprising: a rotationally drivable drum (12), at least one stationary outer drum (19) which extends at least over part of the length of the drum (12), and a circulating line (21) having at least one filter (22) is assigned to the at least one outer stationary drum (19).
 12. The apparatus as claimed in claim 11, further comprising a plurality of treatment liquid outflows (27, 28) assigned to the circulating line (21), wherein at least one of the plurality of treatment liquid outflows (27, 28) can be shut off.
 13. The apparatus as claimed in claim 11, further comprising an upper outflow arranged in the region of the surface (49) of the treatment liquid in the drum (12) and the outer drum (19) and another outflow (28) provided in the region of the bottom (20) of the respective outer drum (19).
 14. The apparatus as claimed in claim 11, further comprising at least one pump (24) provided in the circulating line (21) downstream of the at least one filter (22), as seen in the direction of flow of the treatment liquid through the circulating line (21).
 15. The apparatus as claimed in claim 11, further comprising an inlet (29), wherein the circulating line (21) is provided, downstream of the pump (24), with the inlet (29) which can be shut off and is for recycling the filtered treatment liquid into the same outer drum (19) from which the treatment liquid was removed for filtering.
 16. The apparatus as claimed in claim 11, further comprising a discharge line (21) on the circulating line (21), wherein at least one collecting tank (31) is assigned to the discharge line (21).
 17. The apparatus as claimed in claim 11, wherein the at least one filter (22) is a gravity filter.
 18. The apparatus as claimed in claim 11, wherein the drum (12) is an elongate cylindrical drum with a plurality of consecutive chambers (15), at least one of the chambers (15) being assigned an outer drum (19). 